Nitrates and Neural Tube Defects Croen et al. Maternal Exposure to Nitrate from Drinking Water and Diet and Risk for Neural Tube Defects

authors investigated the association between maternal periconceptional exposure to nitrate from drinking water and diet and risk for neural tube defects. The mothers of 538 cases and 539 nonmalformed controls were interviewed regarding residential history, consumption of tap water at home, and dietary intake during the periconceptional period. Dietary nitrate exposure was not associated with increased risk for neural tube defects. Exposure to nitrate in drinking water at concentrations above the 45 mg/liter maximum contaminant level was associated with increased risk for anencephaly (odds ratio (OR) = 4.0, 95 % confidence interval (CI): 1.0, 15.4), but not for spina bifida. Increased risks for anencephaly were observed at nitrate levels below the maximum contaminant level among groundwater drinkers only (OR = 2.1, 95 % CI: 1.1, 4.1 for 5–15 mg/liter; OR = 2.3, 95% CI: 1.1, 4.5 for 16–35 mg/liter; and OR = 6.9, 95 % CI: 1.9, 24.9 for 36–67 mg/liter compared with <5 mg/liter). Adjustment for identified risk factors for anencephaly did not substantially alter these associations, nor did control for maternal dietary nitrate, total vitamin C intake, and quantity of tap water consumed. The lack of an observed elevation in risk for anencephaly in association with exposure to mixed water containing nitrate at levels comparable with the concentration in groundwater may indicate that something other than nitrate accounts for these findings. Am J Epidemiol 2001;153:325–31. abnormalities, congenital; anencephaly; water pollutant